Tuleks mainida ka, et ta oli Modena hertsogiriigi trooninõudleja.
In the end, Francesco V drew a will in 1875 that appointed as universal heir the 12-year old archduke Franz Ferdinand, eldest son of Emperor Franz Josef's eldest surviving brother Karl Ludwig. (See an excerpt of the will). The will imposed a number of conditions on him and his successors, namely to change his name to "Austria-Este", to adopt the arms of Este, to learn Italian, to avoid marriages with non-Catholic princesses. Should Franz Ferdinand decline, his brothers Otto and Ferdinand would be called, and if they also declined, the inheritance would be shared by the duke of Madrid and the duke of San Jaime (with the same conditions!). Anyone refusing in the future to accept these terms would be immediately by-passed in favor of the next heir. How the inheritance was to pass among future heirs is not described in the secondary source I used.
Accordingly, Franz Ferdinand was styled at the Austrian court Erzherzog von Österreich-Este (see, e.g., Hof- und Staats-Handbuch der Österreichisch-Ungarischen Monarchie for the year 1889, when Rudolf was still alive). Under the terms of the 1753 convention, Modena and Austria could not be united on the same head. This required that the Este inheritance pass to the next available heir, should the archduke holding the title become Austrian emperor. After the suicide of the emperor's only son Rudolf in 1889, and the death of the emperor's brother Karl Ludwig in 1896, Franz Ferdinand became heir presumptive, but he never received any official title as heir. In the end, he never reigned, since he was assassinated in 1914, before the death of Franz Josef, leaving a male issue by a morganatic marriage (the dukes of Hohenberg: they would probably be excluded under the terms of Francesco V's will, but not necessarily under those of the duchy of Modena). Franz Ferdinand's brother Otto (1865-1906) had left two sons, the eldest Karl (1887-1922) inherited the Este claim and was styled Erzherzog von Österreich-Este.